1. Field of the Invention
The present invention relates to a head slider for recording information onto a recording medium and reproducing the same therefrom in a magnetic disk device, an optical disk device, a photo-magnetic disk device or others, while flying above the recording medium or coming into contact therewith, and a method for producing the same, particularly to a method for forming a rail portion of the slider head wherein a head for recording and reproducing information is parallel to the surface of a confronting surface of the medium.
2. Description of the Related Art
As one means for reducing the production cost of an assembly of a head and a support spring, the inventors of the present invention have proposed a non-machine-processed slider, as disclosed in Japanese Unexamined Patent Publication No. 8-235527, which corresponds to a U.S. patent application Ser. No. 08/603,257, and therefor incorporate the contents thereof in this applications. According thereto, a proposed thin film magnetic head slider has an air bearing surface flying above a recording medium or coming into contact therewith where a thin film-forming surface of a thin film magnetic head element is parallel to the air bearing surface and is characterized in that a slider plate, made of a conductive material and having a rigidity, and at least one terminal pad, made of a conductive material, are arranged at a predetermined distance in the direction parallel to the air bearing surface.
Further, a proposed method, for forming such a thin film head slider comprises a process for forming the configuration of the air bearing surface on the substrate over a sacrificial layer or forming a sacrificial layer on a layer defining the configuration of the air bearing surface, a process for forming a flying rail made of an inorganic material on the sacrificial layer, a process for forming the slider plate and the terminal pad by a plating on the sacrificial layer, and a process for separating the slider plate from the substrate by etching the sacrificial layer.
More concretely, Japanese Unexamined Patent Publication No. 8-235527 proposes the following two methods for forming the rail portion as described below.
FIG. 9 illustrates a so-called guppy-shaped slider wherein a slider body 20 has a pair of right and left rails 21, 22 and a single central rail 23 provided on the air-entrance side as seen in the media opposing surface, each of which rails has a taper portion 21a, 22a or 23a, respectively, on the entrance side. A layer defining a mold for forming the respective rails is used for forming the slider as shown in FIG. 10. That is, the mold 30 has recesses 31, 32 for forming the right and left rails 21, 22 and a recess 33 for forming the central rail 23, as well as taper portions 31a, 32a and 33a corresponding to the taper portions 21a, 22a and 23a, respectively.
FIGS. 11 and 13 are cross-sectional views of a rail portion along a plane XI--XI in FIG. 10, formed by first and second conventional methods, respectively. FIGS. 12 and 14 illustrate the steps for forming the rail according to the first and second conventional methods, respectively.
According to the first conventional method, both of a planar portion and a taper portion in the rail are formed of a metallic layer. That is, in FIG. 11, reference numeral 20 denotes a slider body (Ni); 40 a substrate; 40a a part of mold consisting of resist; 41 a layer (Al) having a taper portion defining a part of mold for a rail; 42 a sacrificial layer (Al); and 43 a media opposing surface layer (SiO.sub.2) opposed to a medium. In FIG. 12, the Al layer 41 is formed on the substrate 40 first, and a photoresist 44 is coated thereon and exposed from above. During the exposure, an area wherein the taper portion is formed is exposed while gradually decreasing the amount of light compared with the other area (see FIG. 12(a)). Then, the photoresist 44 is cured with heat or ultraviolet ray to form a taper portion 44a of the photoresist 44 (see FIG. 12(b)). Next, The Al layer 41 is etched by means of ion-milling, sputter-etching or another method (see FIG. 12(c)). The Al layer 41 is completely removed by the etching from an area in which no photoresist is left, but is left in the other area in which the photoresist 44 is still present, wherein an extent of etching varies in accordance with a residual amount of the photoresist 44. Thus, the taper portion 41a is formed in the Al layer 41 (see FIG. 12(d)).
In the above first method, the sacrificial layer 42 of Al (FIG. 11) is formed while using, as a mold, the substrate 40 on which the Al layer 41 having the taper portion 41a is formed in an area corresponding to the rail recess 31 (FIG. 10). Then, the media opposing surface layer (SiO.sub.2) 43 is formed thereon and the slider body 20 is formed by means of nickel-plating or another method. In a post process, the sacrificial layer 42 is removed to result in the slider 20 provided with the rails 21, 22 and 23 (see FIG. 9).
According to the second method, both of a planar portion and a taper portion in the rail are formed of a photoresist. That is, in FIG. 13, reference numeral 20 denotes a slider body (Ni); 40 a substrate; 40a a part of mold consisting of resist; 42 a sacrificial layer (Al); and 43 a media opposing surface layer (SiO.sub.2), and a photoresist layer 44 is formed as a layer having a taper portion used as a part of mold for rails. In FIG. 14, a photoresist 44 is coated on the substrate 40 and exposed from above. During the exposure, an area wherein the taper portion is formed is exposed while gradually decreasing an amount of light compared with the other area (see FIG. 14(a)). Then, the photoresist 44 is cured with heat or ultraviolet ray to form a taper portion (see FIG. 14(b)). This is used as a mold.
In such a manner, according to the second method, while using, as a mold, the substrate 40 carrying the photoresist layer having the taper portion 44a in an area corresponding to the rail recess 31 (FIG. 10), the sacrificial layer 42 of Al is formed thereon. Then, the media opposing surface layer (SiO.sub.2) 43 is formed and the slider body 20 is formed thereon by means of nickel-plating or another method. In a post process, the sacrificial layer 42 is removed to result in the slider 20 provided with the rails 21, 22 and 23 (see FIG. 9).
The first method is advantageous in that the shaping accuracy of the rail is facilitated and the adhesive property to the sacrificial layer coated thereon is enhanced.
The second method is advantageous in that the surface roughness of the rail is minimized, since there is no need to use ion milling.